Poor Separation Research Articles

Photocatalytic degradation of sulfamethoxazole over S-scheme Fe2O3/g-C3N4 photocatalyst under visible light

The application of promising g-C3N4 has been limited by poor photogenerated electron-hole separation and limited absorption for visible light. Sulfamethoxazole (SMX) is a typical antibiotic drug that is used worldwide and hard to be disposed through conventional wastewater treatment methods. Herein, S-scheme Fe2O3/g-C3N4 heterojunction was successfully prepared via a facile one-step sintering method and applied to photodegrade SMX under visible light irradiation. The integration of Fe2O3 and g-C3N4 shows superior charge separation and light absorption ability. As a result, the removal efficiency of 11 wt% Fe2O3/g-C3N4 reaches to 99.2% within 30 min, which is visibly higher than 59.5% of pure g-C3N4. ·O2− and ·OH are demonstrated to be the predominant active species for SMX photodegradation, and the possible degradation pathway is also proposed based on electronic band structure of Fe2O3/g-C3N4 heterojunction. This study presents a facile construction of g-C3N4 based S-scheme photocatalyst and offers an environmentally friendly approach to effectively remove organic pollutants using renewable solar energy.

Regenerable planting of multifunctional amine: Regeneration-enhanced antifouling/antiscaling properties and performance of thin film composite nanofiltration membrane

The problems of poly(piperazineamide)-based thin film composite (TFC) nanofiltration (NF) membrane are the fouling, scaling and poor separation performance of uncharged organics and heavy metal ions. Permanent surface modification lowers the fouling/scaling problems. However, these problems persist as the separation progresses. We address these issues by the on-demand regenerable planting of polyethyleneimine (PEI) into the polyamide (PA) layer of TFC NF membrane. The regenerable planting is based on the electrostatic interaction among the protonated amine groups of low molecular weight PEI and ionized carboxylic acid groups situated at the relatively inner sites (low dielectric constant) of the PA network. The incorporated PEI chains are stable at the pH range of 3–9. The PEI incorporated membrane exhibits significantly enhanced antifouling/antiscaling property, rejection of heavy metal ions (98–99%) and bisphenol A (BPA, 95%) without much negatively affecting the bivalent anion rejection (Na2SO4, 97.5%) and water permeance (11 L m−2 h−1 bar−1) as compared to the pristine and commercial membranes (55–82%, 50–76% and 98–99% rejections of heavy metal ions, BPA and Na2SO4). Advantageously, PEI chains are removable at pH ≤ 2 or pH ≥ 9.5 without affecting the main PA layer. The multiple removal and re-generation of the membrane have been achieved. The flux recovery of the membrane after antifouling/antiscaling tests significantly improved upon intentional removal and reincorporation of PEI. Inherent properties of the modified membrane channels couple with the on-demand regenerable ability show immense promises of the membrane in the separation applications.

Hybrid CdSe/ZnS Quantum Dot-Gold Nanoparticle Composites Assembled by Click Chemistry: Toward Affordable and Efficient Redox Photocatalysts Working with Visible Light.

A new modular, easy-to-synthesize photocatalyst was prepared by assembling colloidal CdSe/ZnS quantum dots (QD) and gold nanoparticles (AuNP) via their ligands thanks to copper-catalyzed azide to alkyne cycloaddition (CuAAC) click chemistry. The resulting composite (QD-AuNP) photocatalyst was tested with a benchmark photoredox system previously reported by our group, for which QD alone acted as a photocatalyst but with a modest quantum yield (QY = 0.06%) and turnover number (TON = 350 in 3 h) due to poor charge separation. After optimization, the QD-AuNP composites exhibited much improved photocatalytic performances: up to five times higher TON (2600 in 3 h) and up to 24 times faster reaction in the first 10 min of visible irradiation. Such an improvement is attributed to an efficient electron transfer from QD to AuNP in the photoexcited QD-AuNP composites, which ensures a much better charge separation than that in QD alone. This was confirmed by studying both (i) the quenching of the QD photoluminescence during the synthesis of the QD-AuNP composites and (ii) the blue shift of the AuNP plasmon absorption band due to the accumulation of up to 7400 electrons per AuNP in QD-AuNP composites under visible light irradiation in the presence of electron donors.

Constructing a tannic-Fe interlayer via a simple in-situ method to enhance the filtration performance of hollow fiber organic solvent nanofiltration membranes

Hollow fiber (HF) organic solvent nanofiltration (OSN) membranes have the advantage of simple production and large packing density, which make them promising for organic solvent recovery. However, current HF OSN membranes still suffer from poor separation performance. To overcome this problem, in this work, we proposed a simple method to in-situ construct a tannic (TA)-Fe interlayer on the surface of an HF ultrafiltration membrane. In this way, we could effectively manipulate the interfacial polymerization (IP) reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC), thus successfully boosting the filtration performance of the polyamide (PA) HF OSN membrane. We highlight that TA molecules were enriched on the surface of the HF ultrafiltration membrane during the phase inversion process, which is beneficial for the in-situ construction of a TA-Fe interlayer via immersing this HF substrate in FeCl3 solution. Consequently, we effectively simplified the fabrication procedure for constructing an interlayer. With the aid of the TA-Fe interlayer, the HF OSN membrane obtained higher crosslinking degree and better filtration performance. The optimized HF OSN membrane achieves an ethanol permeance of 14.7 L m−2 h−1 MPa−1 and a Rhodamine B (RDB, 479 Da) rejection of 98.6 %. Additionally, it displays excellent operation stability performance. It remains an ethanol permeance of 8.6 L m−2 h−1 MPa−1 and an RDB rejection of 99.4 % after a continuous cross-flow filtration for over 1000 min. Also, it shows excellent chemical stability performance, corresponding to an extension of less than 4 % after soaking in ethanol for 8 d. This research shows a simple approach for the fabrication of interlayered thin film composite (iTFC) HF OSN membranes.

ZrO2 modification of homogeneous nitrogen-doped oxide MgTa2O6−xNx for promoted photocatalytic water splitting

Homogeneous nitrogen-doped oxides are of wide visible light utilization for promising photocatalytic water splitting to produce hydrogen, but currently the poor charge separation severely limits their photocatalytic performances. In this work, a homogeneous nitrogen-doped tunneled oxide of MgTa2O6−xNx with an absorption edge of 570 nm was selected as a prototype to investigate the influence of ZrO2 modification on the charge separation as well as photocatalytic performance. It is interesting to observe that the formation of the reduced tantalum species, regarded as recombination centers, in the MgTa2O6−xNx sample could be effectively inhibited via the surface passivation with ZrO2 nanoparticles, based on which the photocatalytic water reduction and oxidation half-reaction activities could be remarkably promoted. Together with modification of the deposited Pt cocatalyst, the optimized H2 evolution rate over Pt-ZrO2/MgTa2O6−xNx (Zr/Ta = 0.10) photocatalyst was almost 4.5 times as high as that of the pristine Pt-MgTa2O6−xNx sample free of ZrO2 modification, whose apparent quantum yield at 420 nm (± 15 nm) achieved herein was superior to those of other reported homogeneous nitrogen-doped photocatalysts. The improved charge separation probably attributes to the introduction of Zr–O–Ta bond after ZrO2 modification, which is helpful to stabilize the tantalum species at more cationic state and inhibit the formation of the reduced tantalum species. This work extends the application territory of ZrO2 modification to the homogeneous nitrogen-doped oxide photocatalysts, and demonstrates its feasibility and effectiveness for remarkably enhanced photocatalytic water splitting performance.

Surface plasmon resonance Bismuth-modified NH2-UiO-66 with enhanced photocatalytic tetracycline degradation performance

For nearly a century, the misuse of antibiotics has gradually polluted water and threatened human health. Photocatalysis is considered an efficient way to remove antibiotics from water. Zirconium-based metal–organic frameworks have attracted much attention as promising photocatalysts for the degradation of antibiotics. However, single Zirconium-based metal–organic frameworks can still not achieve a more satisfactory photocatalytic efficiency, due to poor light absorption and charge separation efficiency. In this study, a novel metal-loaded metal–organic frameworks material was explored. As a potential photocatalytic material, the performance of NH2-UiO-66 in the photocatalytic degradation of tetracycline was greatly improved just by the loading of a single metal. Bismuth/NH2-UiO-66 photocatalysts of various compositions were physicochemically (TEM, SEM, XRD, XPS, BET, FTIR, UV–VIS, PL), and electrochemically (electrochemical impedance spectroscopy, photocurrent response) characterized. We evaluated the photocatalytic performance of Bismuth/NH2-UiO-66 composites by measuring their ability towards tetracycline decomposition in simulated sunlight irradiation conditions. The experimental results indicated that the introduction of metal Bismuth significantly boosts the photocatalytic activity of the composite catalysts. The final degradation rate of Bismuth/NH2-UiO-66 for tetracycline was found to be 95.8%, namely 2.7 times higher than pure NH2-UiO-66. This behavior is due to the surface plasmon resonance effect of Bismuth, which ameliorates the photocatalyst's electron-hole separation and strengthens the charge transfer. Apart from that, the presence of Bismuth magnifies the visible-light absorption range of Bismuth/NH2-UiO-66. In this study, an innovative approach for designing efficient and cost-effective metal-modified metal–organic frameworks photocatalysts is proposed.

Pyrometallurgical recovery of zinc and valuable metals from hazardous blast furnace dust via self-reduction roasting: Phase transformations and morphological evolution

Blast furnace dust (Zn–Fe dust) containing high heavy metal contents is a hazardous waste, and it is derived from the gravity dust removal system and bag dust removal system of a blast furnace. This study elucidated the underlying reasons for the poor separation of Zn and Fe and recommended conditions for the carbothermic reduction roasting process. The results indicated that the poor efficiencies for Zn and Fe separation from Zn–Fe dust were caused by the formation and gradient reduction of wustite (FeyZn1-yO). A higher reduction temperature, longer reduction time and basicity created an advantageous environment for reduction of the wustite intermediate phase and enabled synergistic catalytic reduction of the wustite phase (FeyZn1-yO and FeyCa1-yO). The formation and reduction of the wustite phase (FeyZn1-yO and FeyCa1-yO) are crucial steps in reduction roasting of olivine (ZnyFe2-ySiO4) and ZnxFe3−xO4 with a spinel crystal structure. After adjusting the experimental parameters, the efficiencies for recovery of Zn and Fe from the Zn–Fe dust reached 95.12 % and 96.55 %, respectively.

Successive performance enhancement on a Ge-Ti codoped α-Fe2O3 with AlOOH modification photoanode for photoelectrochemical water splitting

The poor charge separation efficiency is the main limiting factor of the α-Fe2O3 photoanode for photoelectrochemical water splitting. In this study, we have discovered that the incorporation of Ge-Ti codoping and AlOOH modification strategies can greatly enhance the charge separation efficiency of the α-Fe2O3 photoanode. By introducing the Ti element, which possesses high conductivity, and further enhancing the charge transfer through Ge doping, we have achieved a synergistic inhibition of charge recombination in the Ge-Ti codoped α-Fe2O3. Additionally, the introduction of AlOOH through modification has led to an increase in the interface band bending, thereby enhancing charge separation by elevating the Fermi band level. Furthermore, through the secondary growth (shorted as SG) of undoped α-Fe2O3 and the incorporation of a NiFeOx cocatalyst, we have successfully adjusted the surface states and reduced the onset potential. Through the collaborative efforts of Ge-Ti codoping, SG, AlOOH modification, and NiFeOx catalysis, we have sequentially optimized the performance of the α-Fe2O3-based photoanode, resulting in an impressive photocurrent density of 3.46 mA cm−2 at 1.23 VRHE, as well as a low onset potential of 0.65 VRHE.

2D Atomic Layers for CO2 Photoreduction.

Artificial photosynthesis can convert carbon dioxide into high value-added chemicals. However, due to the poor charge separation efficiency and CO2 activation ability, the conversion efficiency of photocatalytic CO2 reduction is greatly restricted. Ultrathin 2D photocatalyst emerges as an alternative to realize the higher CO2 reduction performance. In this review, the basic principle of CO2 photoreduction is introduced, and the types, advantages, and advances of 2D photocatalysts are reviewed in detail including metal oxides, metal chalcogenides, bismuth-based materials, MXene, metal-organic framework, and metal-free materials. Subsequently, the tactics for improving the performance of 2D photocatalysts are introduced in detail via the surface atomic configuration and electronic state tuning such as component tuning, crystal facet control, defect engineering, element doping, cocatalyst modification, polarization, and strain engineering. Finally, the concluding remarks and future development of 2D photocatalysts in CO2 reduction are prospected.

Ni(II)-doped CuWO4 photoanodes with enhanced photoelectrocatalytic activity

CuWO4 has emerged in the last years as a ternary metal oxide material for photoanodes application in photoelectrochemical cells, thanks to its relatively narrow band gap, high stability and selectivity toward the oxygen evolution reaction, though largely limited by its poor charge separation efficiency. Aiming at overcoming this limitation, we investigate here the effects that Cu(II) ion substitution has on the photoelectrocatalytic (PEC) performance of copper tungstate. Optically transparent CuWO4 thin-film photoanodes, prepared via spin coating and containing different amounts of Ni(II) ions, were fully characterized via UV–Vis spectroscopy, XRD and SEM analyses, and their PEC performance was tested via linear sweep voltammetry, incident photon to current efficiency and internal quantum efficiency analyses. From tests performed in the presence of a hole scavenger-containing electrolyte, the charge injection and separation efficiencies of the electrodes were also calculated. Pure-phase crystalline and/or heterojunction materials were obtained with higher PEC performance compared to pure CuWO4, mainly due to a significantly enhanced charge separation efficiency in the bulk of the material.Graphic abstract

Enhanced photoelectrochemical performance of cobalt phosphate modified GaN-ZnO Nanowires/GaN microrods heterostructure photoanode by vacancy defect modulation

Gallium-zinc oxynitride solid solution has been considered as a promising candidate material for photoelectrochemical (PEC) water splitting. However, its PEC performance is severely limited by the poor charge separation efficiency and the adverse intrinsic vacancy defects. Herein, to solve these problems, we developed a novel strategy for constructing dendritic (GaN)1-x(ZnO)x/GaN arrays with type-Ⅱ heterojunction on a conductive GaN crystalline substrate by an Au-assisted chemical vapor deposition method. Then, an additional annealing treatment in Ar is carried out to further decrease the density of surface oxygen vacancy and to increase the density of ON-VGa vacancy complexes for enhancing photoelectrochemical performance. Under the synergistic effect of type-Ⅱ heterojunction and vacancy modulation, the optimized (GaN)1-x(ZnO)x/GaN photoanode exhibits a photocurrent density of 0.25 mA cm−2 at 1.23 V vs. RHE and the surface modification with CoPi co-catalyst can further increase the photocurrent density to 0.45 mA cm−2 at 1.23 V vs. RHE. It is demonstrated that the ON-VGa vacancy complexes are beneficial to increase the PEC performance of gallium zinc oxynitrides.

Defect-free PEO membrane fabrication by hydrogen bonding coupling thermal annealing for carbon capture

Reduction of CO2 emission is an urgent global demand to deal with the current extreme climate and ecosystem destruction. Polyethylene oxide (PEO) is an ideal material for CO2 separation membranes, because of its moderate affinity for CO2. However, due to its high tendency of crystallization, the mass transfer of CO2 is significantly hampered, resulting in poor separation performance. This study proposed of employment of trehalose as the filler to PEO membrane with subsequent thermal annealing, that is hydrogen-bond suppression crystallization coupling thermal annealing healing defects strategy, to simultaneously enhance the gas transport and selectivity. The trehalose plays the role of suppressing PEO crystallization while thermal annealing charges for healing defects. Consequently, the optimized trehalose-loaded PEO membrane exhibits a CO2 permeability of 117 Barrer and an ideal CO2/N2 selectivity of 51, which is superior to the pure PEO membrane. Moreover, the membrane offers merits of anti-plasticization feature and long-term running stability.

Correlation Between Sociocultural and Economic Factors in Pediatric Patients' Families and Emergence Delirium.

Postoperative delirium is a commonly encountered condition that can arise from multiple factors, and its occurrence varies based on the type of surgery in pediatric patients. This study aimed to investigate the occurrence of delirium during the recovery from anesthesia in children undergoing eye surgery and its association with the sociocultural and economic status of their families. This prospective observational study included children aged 2-12 years who underwent eye surgeries. Demographic data, socioeconomic and educational status of parents, parental separation and cooperation scores, Cravero agitation score, and face, legs, activity, cry, and consolability (FLACC) score (at zero, five, 15, and 30 minutes in the postoperative period) were recorded. Patients who scored 5 on the Cravero agitation scale for at least five minutes were considered to have postoperative delirium. The STROBE checklist was followed for reporting. A total of 104 patients were included in the study, of which 65 were male. The mean age of the patients was 6.5±2.9 years, and 42 patients (40.4%) belonged to the preschool age group. The incidence of delirium was found to be 51.9%. Delirium was found to be associated with postoperative pain (p=0.003), age (p=0.001), preoperative anxiety (not cooperative examination score (p=0.047), poor separation score (p=0.006)), presence of a surgical history (p=0.012), and cataract surgery (p=0.007). No evidence was found to demonstrate a link between sociocultural and economic conditions and the development of delirium. This study identified several factors that influenced the occurrence of delirium, including postoperative pain (FLACC≥4), younger age (<6 years), cataract surgery, presence of surgical history, examination score (score 3, not cooperative), and separation score (scores 3-4, poor).

Evaluation of ethanol-based aqueous two-phase systems performance for application in centrifugal partition chromatography (CPC)

Aqueous two-phase systems (ATPS) have recently been proposed for Centrifugal Partition Chromatography (CPC). This type of biphasic system has several advantages over conventional aqueous-organic liquid–liquid systems, namely, high biocompatibility owing to its large water content. The most commonly used ATPS are polymer-based systems. However, owing to their poor phase separation hydrodynamics compared to aqueous-organic systems, the use of short-length water-miscible alcohols has been evaluated as an alternative to polymers. In this study, an ATPS composed of ethanol and dipotassium hydrogen phosphate (K2HPO4) is proposed to overcome the common hydrodynamic drawbacks of polymer-based ATPS. The Ethanol/K2HPO4 system exhibited a very short settling time (ts = 30.85 ± 0.80 s), high interfacial tension (IFT = 6.38 mN/m), significant density differences between the phases (Δρ = 353.40 kg/m3), and low viscosity of the coexisting phases at 25 °C (maximum µ = 3.79 ± 0.11 mPa.s), making it an ideal choice for implementation in CPC apparatus. A comprehensive study of this biphasic system was conducted using CPC equipment by carefully adjusting the operating parameters, specifically, the mobile phase flow rate (F), rotational speed (ω), and mode of operation, that is, ascending (upper phase is mobile) or descending (lower phase is mobile). In this particular CPC equipment, the use of polymers as phase-forming compounds in ATPS resulted in higher CPC pump pressures compared to ethanol or phosphate salt aqueous solutions, thus confirming the superior performance of the ethanol/salt ATPS. The results obtained using this ATPS demonstrated that high F and ω values lead to lower stationary phase retention (SF) and higher backpressures, respectively. SF remained relatively constant and above 50% for F ≤ 6 mL/min but significantly decreased for F > 6 mL/min. This trend confirms that hydrostatically stable conditions can be achieved by employing the Ethanol/K2HPO4 system in the CPC mode by controlling F (i.e., the hydrodynamics of the mobile phase). The partition of the model solutes gallic acid and L-tyrosine was also evaluated using the ethanol/K2HPO4 system. The critical operating CPC parameters were compared, confirming the significant potential of the ethanol/salt ATPS for successful commercial application of this chromatographic technique in the separation of small value-added biomolecules.

Asymmetric Additive‐Assisted Organic Solar Cells with Much Better Energy Harvesting and Wireless Communication Performance

AbstractOrganic solar cells (OSCs), exhibiting better sensitivity to different light intensities and higher power conversion efficiencies (PCEs) under indoor illumination, have great potential to be simultaneously used for solar energy harvesting and optical communication. However, the poor intrinsic molecular stacking and phase separation in active layers significantly hinder the charge transport and extraction in OSCs for achieving this aim. Here, an effective heterohalogen‐substitution asymmetric additive strategy is proposed to fine‐tune the non‐covalent interaction with nonfullerene molecules and optimize the morphology of active layer, which greatly boosts both the OSC photovoltaic performance with the PCEs of up to 18.30% and 29.52% under AM 1.5G and indoor light illumination respectively, and the ‒3 dB communication bandwidths of 4.11, 3.14, and 3.04 MHz at red, green, and blue (RGB) wavelengths respectively. Of particular note, combining the wavelength division multiplexing and adaptive bit‐loading technologies, the visible light communication system comprised of the RGB light sources and additive‐treated OSCs delivers more remarkable data throughput of 302.7 Mb s−1 and higher harvesting power of 7.38 mW simultaneously, presenting an excellent self‐powered capability for enhanced endurance. This work demonstrates that high‐performance OSCs with excellent energy harvesting and wireless communication capacity can be perfectly achieved by a heterohalogen‐substitution asymmetric additive strategy.

Fabrication of multi-morphological Bi2O2(OH)NO3-BiVO4 Z-Scheme heterojunction for enhanced photocatalytic antibiotic removal performance

Due to the suitable band gap, good stability, and convenient preparation, bismuth vanadate (BiVO4) is regarded as one of potential semiconductor photocatalyst. However, the practical application was restricted by low catalytic efficiency and the poor charge separation. To address these obstacles, a novel Bi-based Bi2O2(OH)NO3-BiVO4 heterogeneous composite was constructed and synthesized by a mild and convenient hydrothermal method. The results of XRD, SEM, XPS, and DRS characterizations indicated that the Bi2O2(OH)NO3-BiVO4 heterogeneous catalyst were prepared successfully. The as-synthesized Bi2O2(OH)NO3-BiVO4 composite had good surface properties and catalytic stability. The results of photocatalytic degradation demonstrated that the tetracycline removal capacity of Bi2O2(OH)NO3-BiVO4 composite was obviously enhanced, and the highest degradation rate could reach 95% after 90 min. The results of quenching experiments revealed that both active species of·OH,·O2- and h+ were involved in the Bi2O2(OH)NO3-BiVO4 catalytic system. The possible degradation pathways for tetracycline degradation were proposed by detecting the intermediate products of the degradation process using UPLC-MS technology. Under the interference of pH, common ions and organic matter in aquatic systems, the degradation system can still remain high degradation efficiency. It shows that the Bi2O2(OH)NO3-BiVO4 composite may be a promising photocatalyst for practical application. The current study provides new insight into developing more effective photocatalysts for antibiotic wastewater treatment.

A Method for Extracting the Tree Feature Parameters of Populus tomentosa in the Leafy Stage

With the advancement of 3D information collection technology, such as LiDAR scanning, information regarding the trees growing on large, complex landscapes can be obtained increasingly more efficiently. Such forestry data can play a key role in the cultivation, monitoring, and utilization of artificially planted forests. Studying the tree growth of artificially planted trees during the leafy period is an important part of forestry and ecology research; the extraction of tree feature parameters from the point clouds of leafy trees, obtained via terrestrial laser scanning (TLS), is an important area of research. The separation of foliage and stem point clouds is an important step in extracting tree feature parameters from data collected via TLS. By modeling the separated stem point clouds, we can obtain parameters such as a tree’s diameter at breast height (DBH), the number of branches, and the relationship between these and other parameters. However, there are always problems with the collected foliated tree point clouds; it is difficult to separate the point clouds into foliage and stems, yielding poor separation results. To address this challenge, the current study uses a deep learning-based method to train a mixture of non-foliated and foliated point clouds from artificially planted trees to semantically segment the foliage labels from the stem labels of these trees. And this study focused on a Chinese white poplar (Populus tomentosa Carr.) plantation stand. At the same time, the method of this study greatly reduces the workload of labeling foliated point clouds and training models; an overall segmentation accuracy of 0.839 was achieved for the foliated Populus tomentosa point clouds. By building the Quantitative Susceptibility Mapping (QSM) model of the segmented point clouds, a mean value of 0.125 m for the tree diameter at breast height, and a mean value of 14.498 m for the height of the trees was obtained for the test set. The residual sum of squares for the diameter at breast height was 0.003 m, which was achieved by comparing the calculated value with the measured value. This study employed a semantic segmentation method that is applicable to the foliated point clouds of Populus tomentosa trees, which solves the difficulties of labeling and training models for the point clouds and improves the segmentation precision of stem-based point clouds. It offers an efficient and reliable way to obtain the characteristic parameters and stem analyses of Populus tomentosa trees.

Study on the hydraulic classification characteristics of micron‐sized silica particles

AbstractThe present study investigates the motion characteristics of micron‐sized silica particles and how solid–water interaction regulates hydraulic classification. Two methods were evaluated for classifying micron‐sized silica particles. Using the small‐diameter cyclone for hydraulic classification of micron‐sized silica particles resulted in poor separation due to the short residence time of particles in the cyclone. Particle settling in still water showed that settling velocity, drag force, and virtual mass force increased with particle size, providing a basis for size classification. In the particle sedimentation process, drag force and gravity were dominant, with drag force reaching equilibrium with gravity in a fast time. The upward water flow was introduced to classify silica particles, with its superficial velocity between the settling terminal velocities of large and small particles, allowing large and small particles to flow to the overflow and underflow, respectively. The upward flow velocity was higher near the center of the flow field and lower near the wall, leading to a parabolic distribution pattern of the particle group along the radial position. In hydraulic sedimentation classification experiments of silica particles, the average particle size of the overflow sample was lower than that of the feed, and its size range was narrower, indicating the feasibility of hindered sedimentation by upward flow for classifying micron‐sized silica particles.

Centrifugation forced ice-concentrate separation to enhance suspension freezing desalination performance

Suspension freeze desalination is a promising route for treatment of high salinity wastewater, but the poor ice-concentrate separation often generates decrease of desalination efficiency. In this work, it is demonstrated that centrifugation forced dewatering can assist in ice purification and enhance suspension freeze desalination performance. The positive correlation and good linear fitting relationship between ice purity and dewatering rate were identified at various centrifugation speeds, centrifugation time, and ice layer thickness. Changes of ice shape were recorded by low-temperature optical microscope observation system. The free water removal and ice floc destruction induced by centrifugal field have an important contribution to ice purification. Increasing centrifugation speed from 100 r/min to 500 r/min, the corresponding relative centrifugal force increased 27-fold, creating sharp increases in ice purity (rate constant k = 0.1605) and dewatering rate (rate constant D = 0.0563). Due to the strong binding characteristics and small portion of bound water, ice desalination efficiency per unit centrifugal force dropped when centrifugation speed increased from 1000 r/min to 3000 r/min. Besides, the multi-step dewatering and purification mechanism involved in ice centrifugation was depicted. The suspension freeze technology hybrid with centrifugation not only enhances desalination efficiency but also is beneficial to obtain high-purity ice.

Flotation Characteristics of Amphibole-Type Oxidized Iron Ore via Reverse Anionic Flotation

To explore the flotation feasibility and flotation law of iron minerals from amphibole-type iron oxide ore with full-size minerals, a systematic study on the flotation behaviors of single minerals hematite, quartz, and amphibole was carried out with the anionic reverse flotation system. The effects of collectors, depressants, activators, and pH on the floatabilities of three single minerals was investigated. The flotation separations of binary mixed minerals and ternary mixed ores were carried out, respectively. The study results show that CaCl2 is adsorbed on the surfaces of quartz and amphibole, which can activate them. The hydroxyl groups of the starch molecular chain were adsorbed on the surfaces of the hematite and amphibole in the form of hydrogen bonds, but were hardly adsorbed on surface of the quartz. Therefore, both hematite and amphibole were depressed, resulting in a poor separation effect of the three single minerals in the anionic flotation system.